Mark 12 build, upper questions...

D

Desert_Spectre

Private
Minuteman
Jul 10, 2010
32
0
38
Western USA Regional
#1
I am currently entrenched in that ever so un-beloved task of grinding dollars to build a new platform... This one being a Mark 12. NOW! since I'm using my good ol' DPMS lower with a few goodies internally that are already there, my concern is over the upper receiver. The one that i was (and am still) considering is the BCM Mark 12 mod 4 assembly, as it is the only one i can find that looks to be half decent... even if its a 1/8 twist rather than the spec 1/7...

I guess what I'm asking is for clear education and some links that i cant seem to find... namely more "authentic" mark 12 upper assemblies, and/or feedback on the BCM's accuracy and weight performance. I plan to run both standard 55gr FMJ's for economy/training purposes, and some flavor of 77gr match ammunition for distance work, hence my concern over the twist rate. I am also concerned that the BCM's "heavy" barrel is more weighty than the so-called "contoured heavy barrel" i read about the spec Mark 12's having, but since i cant find any hard data, I am skeptical. Weight is a concern because this platform must be maneuverable enough to run with my team in any role and i wish to optimize my choice accordingly.

I'm sure i forgot something I was going to ask, but that's it for right now at least...

Thank you very much for your time!
 
#4
Re: Mark 12 build, upper questions...

You cant go wrong with High Caliber Sales. He works with AJ Brown who is also a Hide Member and a excellent gun smith. AJ spent many years with Crane Naval Surface Warfare Center and has spent ALOT of time working on and I beleive testing the MK12 weapon system. If you decide to build one yourself you can always just contact him with any questions you have and Im sure he would have all the answers you need and more.
 
#5
Re: Mark 12 build, upper questions...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DesertSpectre</div><div class="ubbcode-body">1. your first link didn't work for me, just sent me to a weird google demo...
2. second link looked to be a fine piece of kit though...
3. what exactly is the "big difference" you are referring to?</div></div> 1. Try it again, it redirects you to a whole bunch of links to posts on here regarding the MK12 MOD 0/1 SPR platform as well as some external links....some good info in some of them.
2. "KJO" is his screename on here and he puts together *proper builds
3. If you are doing a MK12 build...you will be using very specific parts vs. if you were doing an SPR build, you could build with whatever parts suited your needs.
 
#7
Re: Mark 12 build, upper questions...

Non pro citizen gun guy here.
Built my own MK12 Mod 0 clone.
1:12 Douglas/Frank White barrel (Compass Lake Engineering)

Uh did I mention it's a .22LR?

The upper was about $1700 plus suppressor (no Ops, inc brake/collar) and optic (a $300 eXplore Optics MKIV clone that focuses to shorter ranges and saves $1100).

It rides a DPMS based Clark Gator lower.

Bad pictures:

http://www.rimfirecentral.com/forums/showthread.php?t=328500
 
#8
Re: Mark 12 build, upper questions...

You have basically two choices here- one, go spec build, or two, DON'T. Once you deviate from the spec, the sky's the limit on how to build an AR-15. ar15.com is the place to go research the best way to build the best zombie blaster.

Once you decide on spec, you can get a turn-key build from highcaliber (Kevin) at the swipe of a visa card, or get an 18" barrel from White Oak and build around that. I'm a Mod 0 fan, just never warmed up to the full quad rail thing. The SWAN rail is something you can skip as well if you aren't a NV owner. It just adds weight.

The folks at PRI are pretty easy to deal with. Holliger's barrel, a USGI flattop receiver, BCG, charge handle, gas tube, and a handful of parts from PRI and you are ready to screw it together.

The HG is where the money goes, cheap stuff versus spec good stuff, when comparing a spec SPR build versus a zombie blaster.

Also keep in mind the spec barrel is a requirement if you want to run the spec suppressor, the Ops Inc 12th Model. It has a shoulder on it to correctly fit the Ops Inc 2 point mount collar.
 
#10
Re: Mark 12 build, upper questions...

Ok, I only have one more concerning question on my researching... I know that the accuracy will suffer with lighter mil-spec rounds, but I'm not made of money and I train a lot in all ranges and forms, what i don't know is, with say, the HC mark 12 mod 1 or similar match-grade workings, other than accuracy loss, using say, XM-193 or M855's wont physically hurt it, will they? I always see "This weapons isn't made for the spec stuff" and other notes when i dabble online, and i don't know if its just noting accuracy loss, or warning me that bullets will do terrible things to the action and barrel, lol...
 
#11
Re: Mark 12 build, upper questions...

Shooting XM193 or M855 won't hurt the gun. Brass is way softer than the steel in the chamber. I doubt that even the steel cased stuff would hurt it, but I won't take that chance with mine. My WOA barreled Mod 0 clone shoots pretty well with XM193 or my 55gr FMJ reloads at 100 yards.
 
#12
Re: Mark 12 build, upper questions...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: skatz11</div><div class="ubbcode-body">Shooting XM193 or M855 won't hurt the gun. Brass is way softer than the steel in the chamber. I doubt that even the steel cased stuff would hurt it, but I won't take that chance with mine. My WOA barreled Mod 0 clone shoots pretty well with XM193 or my 55gr FMJ reloads at 100 yards. </div></div>How well?
 
#13
Re: Mark 12 build, upper questions...

The thing I would be worried about, if you use an expensive custom barrel, is using the gun like a carbine when you're training and getting premature barrel wear on an expensive barrel. If you wanted a more run-N-gun style upper I would go with a cheaper barrel is all.

The only reason I bring this up is for me when I'm "training" with a precision gun, I still use match/hand-loaded ammunition, I've really got no use for FMJ ammo. I'm not sure what you want this gun to be. Of course if barrel life is not a concern, then just run it however you want.
 
#14
Re: Mark 12 build, upper questions...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Oodin</div><div class="ubbcode-body">The thing I would be worried about, if you use an expensive custom barrel, is using the gun like a carbine when you're training and getting premature barrel wear on an expensive barrel. If you wanted a more run-N-gun style upper I would go with a cheaper barrel is all.

The only reason I bring this up is for me when I'm "training" with a precision gun, I still use match/hand-loaded ammunition, I've really got no use for FMJ ammo. I'm not sure what you want this gun to be. Of course if barrel life is not a concern, then just run it however you want. </div></div>

I very much appreciate your advice on this point! Once I settle into a steady pattern, i will prolly run handloads ((currently still a reloading virgin, lol)) but for now, barrel life isn't my largest concern....

Thank you all for your help!
 
#15
Re: Mark 12 build, upper questions...

As stated earlier,High Caliber sales is very GTG. Kev works with you and they put out a fantastic product. That said, I'm pretty sure he only does the mod 1 and not the zeros. I love mine.
 
#16
Re: Mark 12 build, upper questions...

I will say, getting the handguard lined up with the receiver and keeping it there while still getting it torqued was a PITA. It has to be perfectly timed or the SWAN sleeve doesn't sit straight.

Then the torque was either under 30 or right up at 80ft/lb to get the nut lined up with the gas tube hole (though there's no gas tube on my .22.

Once the nut's on straight and tight, tightening the handguard nut while keeping the handguard rail aligned with the receiver rail was the most fiddly problem.

Wound up with the receiver in the action/bench vise (Brownell's), and two Sears strap wrenches on the big aluminum handguard nut and handguard, pushing in opposite directions.
 
#17
Re: Mark 12 build, upper questions...

I was gonna make another thread on this question, but then thought that I didn't want to be "spamming" the main page with my noob BS, lol... I have a decent trigger on my lower at the moment, but it is on the carbine-flavored heavy side... I know that the spec mark 12 gets a two stage KAC trigger apparently, but as I can go with whatever i wish, I wanted other opinions...

Is a two-stage like the KAC good for a rough-and-tumble. multipurpose field weapon, or would i be better off with a semi-light single stage? I ask based on the fact that i have zero experience with two-stage triggers and am still not entirely sure how they work...
 
#18
Re: Mark 12 build, upper questions...

If it is good enough for the guys the MK12 was designed for; it just may be good enough for you?? Or you could be one of those that think the military goes w/ the cheapest bidder! I am going w/ the KAC from Highcaliber and they are getting hard to find.
 
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